Before you jump to conclusions...
Apple are now viciously strict with their ship dates, but any of us who've ever done it know that software development rarely produces something on time. A conspiracy theory is far less likely than a good old schedule crunch: these are features that most likely missed the code-freeze.
Take this scenario:
The iProduct features require improvements to the Virtual keyboard, there are bugs in some east-Asian locales, and there's a feature requirement for X9-like input too.
The dev team starts pulling apart the keyboard code, adding the new features and fixes simultaneously. The X9-alike is to be a user-selectable option, so it's governed by a preference selector.
Release comes nearer, and the system is ready to freeze, most of the virtual keyboard library is fine, and some critical bugs in, say, Thai input have been fixed, and need to be rolled out.
However, but the X9-ish stuff just isn't working out - maybe it leaks memory, maybe it has poor responsiveness, maybe it doesn't insert the word "cunninlingus" in at the most inappropriate place, like the regular keyboard does. Whatever the reason, it needs another two weeks, and there's no way they're going to stall iOS 5 for that.
So the option now is to either unpick the code for X9, and risk destabilising the stuff that works, or hide the preference that turns it on. Apple are pretty good at making software, so which do you think they do?